//==============================================================================
//	
//	Copyright (c) 2002-
//	Authors:
//	* Vojtech Forejt <vojtech.forejt@cs.ox.ac.uk> (University of Oxford)
//	
//------------------------------------------------------------------------------
//	
//	This file is part of PRISM.
//	
//	PRISM is free software; you can redistribute it and/or modify
//	it under the terms of the GNU General Public License as published by
//	the Free Software Foundation; either version 2 of the License, or
//	(at your option) any later version.
//	
//	PRISM is distributed in the hope that it will be useful,
//	but WITHOUT ANY WARRANTY; without even the implied warranty of
//	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//	GNU General Public License for more details.
//	
//	You should have received a copy of the GNU General Public License
//	along with PRISM; if not, write to the Free Software Foundation,
//	Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//	
//==============================================================================

package com.prism.e4.rcp.prism;

import java.util.Arrays;
import java.util.Comparator;

/**
 * A class that allows to compare points w.r.g. a lexicographic order. The order
 * of elements is given by the array {@code dimensionPermutation} passed in the
 * constructor {@link #PermutedLexicographicComparator(int[])}.
 * <p/>
 * Note that the comparator is only capable of comparing points with equal
 * dimension. This probably violates the specification of the {@link Comparator}
 * class, but it shouldn't be any problem as comparing points of different
 * dimensions makes no sense in our case.
 */
public class PermutedLexicographicComparator implements Comparator<Point> {
	private int[] permutation;
	private boolean[] increasing;

	/**
	 * Creates a new instance of the comparator.
	 * 
	 * @param dimensionPermutation
	 *            The order of coordinates, the length of the array must be
	 *            equal to the dimension of points to be compared. For example,
	 *            supposing the dimension of points to compare is 3, the array
	 *            [2,0,1] says that the lexicographic order should be used in
	 *            which the last coordinate has the highest priority, and then
	 *            the first two follow.
	 * @param increasing
	 *            if increasing[i] is true, then the ith dimension will be used
	 *            such that the points with the smaller values go first,
	 *            otherwise they go last
	 */
	public PermutedLexicographicComparator(int[] dimensionPermutation,
			boolean[] increasing) {
		// check that the array is a valid permutation
		int[] clone = dimensionPermutation.clone();
		// TODO check size etc.
		this.increasing = increasing;
		Arrays.sort(clone);
		for (int i = 0; i < clone.length; i++)
			if (clone[i] != i)
				throw new IllegalArgumentException(
						"The array is not a valid permutation");
		this.permutation = dimensionPermutation;
	}

	@Override
	public int compare(Point o1, Point o2) {
		// check if the input is allowed;
		if (o1.getDimension() > permutation.length
				|| o2.getDimension() > permutation.length)
			throw new ClassCastException(
					"The dimension of the point is greater that comparator's dimension");

		if (o1.isCloseTo(o2))
			return 0;

		return compare(o1, o2, 0);
	}

	/**
	 * Compares two points, starting with the coordinate with the {@code i}-th
	 * highest priority.
	 * 
	 * @param o1
	 * @param o2
	 * @param i
	 * @return
	 */
	protected int compare(Point o1, Point o2, int i) {
		int dim = this.permutation[i];
		if (o1.getCoord(dim) < o2.getCoord(dim))
			return (increasing[dim]) ? -1 : 1;
		else if (o1.getCoord(dim) > o2.getCoord(dim))
			return (increasing[dim]) ? 1 : -1;
		else
			return compare(o1, o2, i + 1);
	}
}

// ------------------------------------------------------------------------------
